Rex Smith

I have a 1991 F150 (inline 6) that I have owned for about 3 years, now. Since owning it - the AC has never worked - AC has simply been "roll down the windows". I'm kind of tired of no AC, now (now that we are hitting 104+ degrees in parts of Texas)... and am ready to make the changes needed to convert from the non-functional R12 system to R134a.

If the compressor still works - would it be usable in a R134 system? Or do I need to replace it with one specifically for R134a?

How about the hoses, lines, and other components? I know about the new fittings I'll need for the Hi & Low sides. (or should I get new lines completely?)

I DO have vacuum gauges and a vacuum pump. I've replaced one of the lines on another truck (Silverado 1500) that had a broken-off schrader valve - vacuumed down the system, made sure it held, then added oil/freon back - and several years later - is running well. So - I'm not completely unfamiliar with the system - but I *do* think I can accomplish it as a DIY - as long as I know I'm getting / working with the right hardware components that I need for R134a systems.

Is there a DIY / How-to that I've missed as yet? Or any simple guidance that can be offered?

Rex S.

wde3477

Perhaps others will chime in with more recent experience - mine dates from a conversion about 20 years ago when conversions were relatively new and instructions were perhaps overly inclusive.
Recommendations at that time were to replace the dryer with a R134 spec, replace the orifice tube for a R134 spec (there's a color convention, but I forgot which color is what), replace all of the O-Rings to a green version, drain the oil in the compressor and replace with an Ester based oil (about 7 ounces from what I remember), remove the low pressure cutout and turn the screw about 1/8 turn CCW to lower the cutout pressure from about 28psi to 22 psi, drain the system and flush, then refill with R134 at about 3/4 of the pounds called for on the sticker.
Had to replace the compressor shortly afterward, but I think it was on its way out anyway. System seemed to work OK, typically had to add 1/2 can per year, but wrote this off due to the original hoses, my lack of expertise with A/C systems, and such. Definitely didn't get as cold as the original Freon, but a step up on the fan speed, and running in Recirc mode kept things comfortable. Typically recharged to get the low side pressure to maintain in the low 30s with fan speed on High.
Perhaps not the textbook correct way to convert, but much better than that 2/60 A/C (that's two windows down at 60mph, for the young'uns :-)~

Rex Smith

Thank you for the info. I'm driving a trailer-load of honeybees across Texas next week - dropping them before the sun comes up - then heading back to Dallas. I'll look into the details of the R134a conversion when I return.

My big concern - was if the compressor doesn't run/work - whether a replacement compressor would HAVE to be made specifically for R134 - or would an OEM/parts store AC compressor that was originally intended for R12 would do the job - just with the correct oil.

Sounds like from your experience, I'll need a new dryer as well as an orifice tube as well... (and o-rings/seals)

rexter

I did (had my mechanic buddy do it) on my '93 last fall
There isn't a r134a specific compressor that I know of.
I picked up a new 4 Seasons compressor, new liquid line, new drier, and a red orifice from Rock Auto. He removed said parts and the cleaned the evaporator and condenser with cleaner and compressed air. Installed new parts and vacuumed/charged it. It is cold enough that on these 100* plus days I have to turn it down to the second fam setting.

You meed the red orifice to raise the pressure for the 134a. People that complained when retrofitting started were using the blue orifice.

digitaltrucker

https://www.google.com/search?site=&...k1.ZWVHVOQs-F0

77Ranger460

I have a R12 vehicle that I changed over to R134A ten years ago. It is still working good.